CLAY, CASSIUS MARCELLUS (1810–1903), American politician, was born in Madison county, Kentucky, on the 19th of October 1810. He was the son of Green Clay (1757–1826), a Kentucky soldier of the war of 1812 and a relative of Henry Clay. He was educated at Centre College, Danville, Kentucky, and at Yale, where he graduated in 1832. Influenced to some extent by William Lloyd Garrison, he became an advocate of the abolition of slavery, and on his return to his native state, at the risk of social and political ostracism, he gave utterance to his belief. He studied law, but instead of practising devoted himself to a political career. In 1835, 1837 and 1840 he was elected as a Whig to the Kentucky legislature, where he advocated a system of gradual emancipation, and secured the establishment of a public school system, and a much-needed reform in the jury system. In 1841 he was defeated on account of his abolition views. In 1844 he delivered campaign speeches for Henry Clay throughout the North. In 1845 he established, at Lexington, Kentucky, an anti-slavery publication known as The True American, but in the same year his office and press were wrecked by a mob, and he removed the publication office to Cincinnati, Ohio. During this and the earlier period of his career his zeal and hot temper involved him in numerous personal encounters and several duels, in all of which he bore himself with a reckless bravery. In the Mexican War he served as a captain of a Kentucky company of militia, and was taken prisoner, while reconnoitring, during General Scott’s advance on the City of Mexico. He left the Whig party in 1850, and as an anti-slavery candidate for governor of Kentucky polled 5000 votes. In 1856 he joined the Republican party, and wielded considerable influence as a Southern representative in its councils. In 1860 he was a leading candidate for the vice-presidential nomination. In 1861 he was sent by President Lincoln as minister to Russia; in 1862 he returned to America to accept a commission as major-general of volunteers, but in March 1863 was reappointed to his former post at St Petersburg, where he remained until 1869. Disapproving of the Republican policy of reconstruction, he left the party, and in 1872 was one of the organizers of the Liberal-Republican revolt, and was largely instrumental in securing the nomination of Horace Greeley for the presidency. In the political campaigns of 1876 and 1880 he supported the Democratic candidate, but rejoined the Republican party in the campaign of 1884. He died at Whitehall, Kentucky, on the 22nd of July 1903.

See his autobiography, The Life, Memoirs, Writings, and Speeches of Cassius Marcellus Clay (Cincinnati, 1896); and The Writings of Cassius Marcellus Clay (edited with a “Memoir” by Horace Greeley. New York, 1848).